It is known to provide vehicles with powered closure panels such as liftgates, decklids, side-doors, tailgates, movable glass panels, hoods, tonneau covers, and others. The power-assisted closure panels may be operated by a number of mechanisms, including without intending any limitation key fob switches, dash panel switches, liftgate switches, motion sensors, voice-command sensors, associated with the closure panels, and others. Typical power controlled closure panels include a power actuator such as a motor and gearing providing sufficient torque to translate the closure panel between an open and a closed configuration. Other conventional power controlled systems include pneumatic cylinders or hydraulic systems having motor-driven fluid pumps, and unpowered mechanical assist components that work in conjunction with a standalone powered motor or actuator.
It is also known to provide lift-assist mechanisms for power controlled closure panels. Such lift assist mechanisms include torsion bars, torsion springs, air spring cylinders, tension springs, counterbalance struts, and others. Lift assist mechanisms reduce the load on the power actuator used to translate the closure panel between the open and the closed configuration. This allows use of much smaller motors, making optimization of performance all the more important and significant in achieving longer component life.
Still more, it is known to provide programmable power-assisted closure panels. As examples, a height to which a power closure panel such as a decklid or liftgate may be pre-programmed or predetermined, to avoid having the panel strike an overlying low surface such as a parking garage roof, sprinkler head, or the like. Moreover, it is known to provide a “stop and hold” function whereby the power closure panel may be stopped manually or automatically such as by a sensor to avoid contacting an obstacle during an opening or closing operation. A representative system providing such a “stop and hold” function is described in U.S. Pat. No. 7,547,058, the entirety of the disclosure of which is incorporated herein by reference.
Various environmental factors may affect power closure panel performance. As non-limiting examples, it is known that extremes of temperature and grade (i.e., a nose-up or nose-down orientation of a vehicle or the angle at which a vehicle is oriented relative to a horizontal plane) affect performance of power closure panels. In such conditions, the torque required for the power assist mechanism increases, and therefore the electrical current draw required by the power actuator likewise increases. For example, when a vehicle is positioned on level ground and/or at normal ambient temperature, a power controlled mechanism must apply a certain amount of opening/closing torque or force and braking to translate the closure panel between an open and a closed configuration. On a grade positioning the vehicle in a nose-down orientation, the closure panel must be pulled “uphill” in order to close the panel, and an increased amount of torque or force is required. On a grade positioning the vehicle nose-up, additional dynamic braking or force is required to prevent the closure panel from overextending during opening. At low temperatures, electrical systems become more efficient and therefore can be operated at a reduced electrical current draw compared to higher temperatures.
For programmable power-assisted closure panel mechanisms, the potential for extremes of temperature and grade must be factored into the programming, i.e. the programming must be configured to compensate for such potential extremes of grade and/or temperature. Conventional programmable power-assisted closure panels must be programmed by trial and error, and attempt to meet all conditions of voltage, temperature, grade, load on gate (for example, snow), etc. using a single performance sensor calibration by way of controlling speed of operation of the lift assist mechanism, for example a strut. Such conventional systems cannot automatically accommodate variations in operating conditions, for example extremes of voltage, temperature, grade, load on gate, etc., which significantly adversely affects the torque required of the power mechanisms and therefore the electrical current draw required for the power actuator to operate the closure panel. A generalized approach to operating a power closure system must ordinarily use current that would be higher than required as these systems have not had the benefit of being customized for the specific conditions of operation, adversely affecting component life.
To solve this and other problems, the present disclosure relates to a performance optimizing system for a power closure panel. The system is configured to adapt to varying conditions of voltage, temperature and grade extremes, and reacts to those conditions by altering the speed of the lift assist mechanism, by adjusting the power required to deliver optimized voltage and current that controls the closure panel opening/closing speed to achieve efficient function despite extreme conditions. The systems further adapt to other variables which can impact closure panel closing force (and thereby the required voltage/current that must be supplied to the power closure panel to ensure a proper panel closing force/speed) such as passenger cabin air pressure and air exhaustion rate. Such an intelligent system, having the environmental input knowledge, would allow for implementation of for example, a SNOW LOAD mode, or other specific conditions where special operating performance parameters are required and are user selectable convenience features.